Script to scale objects resets scale when scrubbing through frames
I'm pretty sure your scale is keyframed. Just like when you scale manually and there are scale keyframes present, it will ignore your changes (unless you use auto-keying) and reset to the scale saved in the keyframe. FBX often have everything keyed by default export options of the program they were created with, even if the property isn't animated. If that's not the case, please don't downvote, but provide more detail, maybe share the .blend. Thank you.